I have two PT-17s, one with a OS 120 and the other with a Zenoah 38 magneto. Both have advantages and disadvantages, the 120 version is a bit lighter and sounds great, but uses expensive glow fuel. The Zenoah is heavier, but uses gas which is a lot cheaper. Forget the 80 as it actually uses about as much fuel at full throttle as the 120 uses at 3/4. You really swing a big prop on the PT-17 to make it fly right. If you need anything bigger I would suggest you go to a gas motor.